This invention relates generally to apparatus for fusing an unfused image to a support by means of heat and pressure. More particularly, this invention relates to fuser apparatus which has release material applied to it across its fusing length in which excess release material accumulated at the ends of the apparatus are redistributed towards the center thereof.
Typically, in the electrographic process an original is illuminated by a light source to form an image which is projected upon a photoconductive member to produce a latent electrostatic image corresponding to the original. The latent image is developed by means of toner particles to produce a toner image which is transferred to a support such as a continuous web or copy sheet of plain paper. The unfused toner image is fixed to the support by means of heat and pressure through contact with a heated fuser member such as a roller. The roller surface is of a material such as polytetrafluoroethylene resin or silicone elastomer which has good release properties to prevent sticking of toner and other debris to it. Typically, a release material such as silicone oil is also applied to the roller surface to improve its release properties.
Release material applied to an elastomeric fuser layer tends to be absorbed, thus causing the elastomer to swell. Where the fuser member contacts supports of different dimensions, such as 11" and 14" paper, differential swelling at the ends of the fuser member occurs if the processing of shorter length supports predominates. When longer supports are then processed, image defects result. Moreover, in such case, release material tends to accumulate at the ends of the fuser member not in contact with the shorter length supports. When longer length supports are run, the excess material is carried off by the first few supports leaving objectionable streaks of release material on the support and making it difficult to write or type on the support.
It is thus desirable that fuser apparatus be provided in which release material may be applied to a fuser member without creating differential swelling of the fuser elastomeric layer, and in which release material applied to the fuser member not build up on the ends of the fuser member when shorter length supports are processed.